XIAO BLE Sense loses COM port on code upload


I am new to microcontrollers and electronics, and I recently bought the XIAO nrf52840 BLE Sense due to it’s small size and whilst most of the board works fine, when I upload code (Blink example program) from the Arduino IDE it uploads fine, but then the COM port for the board disappears and I am then unable to upload code.

When I double press the reset button the board is recognised as a USB drive with 3 files on it and I am then able to upload code, (I assume this is what people mean by bootloader) and then it reverts back to being in the previous state it was in.

Whilst I probably could tediously use the board like this, it seems inconvenient to develop code on, is there a fix for this issue?


yes, unfortunatly this is how it works…

some things you may try… I have found that if you lower the serial baud rate to something reasonable, like 19200 or 9600 sometimes the xiao will accept new programming without pressing the button

also look into Arduino OTA… this is a way to upload code over the wifi link

also you can try to use the XIAO expansion board, it has a reset button which is a little easier to press

Hi there,
Go try one of the DRAG and DROP files from the Thread Named 🤠 Xiao Expansion board drag & drop testing uf2 flash files
Grab the ZIP for the RGB LED tester.
Drop the Uf2 file on the Xiao in File explorer (bootloader) once it’s flashing the RGB unplug and replug and Identify the New com port. It should now allow you to upload without Bootloader mode.
Some of the older examples may nerf up the map of the flash & bootloader as well as if you send it Garbage code too it will happen. This tech cleans that right up. YMMV
GL :slight_smile: PJ